1. Field of Invention
The invention relates to a brake mechanism for a vehicle, in particular an agricultural utility vehicle.
2. Description of Related Art
In the case of agricultural utility vehicles, brake mechanisms are used which can comprise a service brake and a parking brake. These service brakes and parking brakes must, in operation, fulfil high performance requirements due to the heavy weight of the utility vehicles and the towing loads. The brake mechanisms, in the case of agricultural utility vehicles, are also provided on the output shaft in the drive train.
The output shaft here has a substantially higher rotational speed in comparison to a wheel speed. Therefore brake disks of the brake mechanism, which are arranged on the output shaft, and stationary brake disks, which are arranged on a rotationally-fixed housing of the brake mechanism, have a high rotational speed difference. Thus during a brake application, undesirably high heat can develop in the brake mechanism due to the friction between the brake disks.
This heat development can be counteracted for example with an annular piston brake, such as for example a cardan brake, integrated into a transmission, by cooling the brake disks. The brake disks are arranged in the brake mechanism in such a way that they are brought into contact with heat-dissipating oil. At the same time the oil quantity necessary for cooling the brake disks may, depending on the arising heat development, be controlled by a pump unit, such as for example a transmission pump. If the rotational speed of the output shaft is high, a larger quantity of oil for cooling the brake mechanism must be supplied by the transmission pump. This larger quantity of oil can only be made available by greater power of the transmission pump. However this increased power of the transmission pump reduces the utility vehicle power that is available overall in the utility vehicle. Therefore the utility vehicle power is affected inter alia by the power required by the transmission pump.